1. Field of the Invention
The present invention relates to a power tool, such as a jigsaw or saber saw, for reciprocally driving a blade.
2. Description of the Related Art
Reciprocal-movement power tools, such as jigsaws and saber saws, cut work pieces by reciprocating a blade. When the work piece is thick, the blade needs to be reciprocated by a large movement amount to produce a large cutting force. On the other hand, when the work piece is thin, it is better to reciprocate the blade by a small movement amount. Problems arise when a power tool with a large reciprocating amount is used to cut a thin work piece. For example, the work piece can be shaken by movement the blade, the cut surfaces can be roughly cut, the work piece can bend, and the blade can break. On the other hand, problems can also arise when a reciprocal-movement power tool with a small movement amount is used to cut a thick work piece. For example, saw dust is not properly removed, clogs can occur because dust is not properly removed, the cut surfaces can be roughly cut, and the life of the blade can be shortened because the same part of the blade is always used.
Japanese Patent-Application Publication Nos. 59-176001 and 2000-225517 disclose reciprocal-movement power tools capable of mechanically changing reciprocal movement amount. However, the power tools disclosed in these publications change the reciprocal movement amount using a complicated mechanism for converting rotational movement of a motor into reciprocal movement for cutting and machining. In addition, these conversion mechanism generate a great deal of vibration and noise.
To solve these problems, it is conceivable to provide a reciprocal-movement power tool with a linear motor and attach the blade to the tip of the drive shaft of the linear motor. However, if a linear motor was used as the drive source for a reciprocating tool, there would be a need to fix the start position of the drive shaft. If the start position is not fixed, then the start position of the drive shaft, that is, the position of the drive shaft before power of the power tool is turned ON, would be determined by where the drive shaft was positioned when power of the power tool was last turned OFF. In this case, when the power is turned ON to start reciprocal movement of the drive shaft, the drive shaft will hit against the housing of the power tool either when the drive shaft moves forward or in reverse. Such a problem is not present in conventional reciprocal-movement power tools, because the range of the reciprocal movement is fixed mechanically by the mechanism that converts rotary movement of a rotary motor into linear movement of the blade.
It is an objective of the present invention to overcome the above-described problems and provide a reciprocal-movement power tool driven by a linear motor, and with no complicated mechanisms for changing reciprocal movement amount.
In order to achieve the above-described objective, a power tool according to one aspect to the present invention includes a linear motor and a maximum reciprocal movement amount setting unit. The linear motor has a movable member driven to move reciprocally. The movable member has a tool connector for connecting work bits to the movable member. The maximum reciprocal movement amount setting unit is for setting maximum reciprocal movement amount at which the linear motor drives movement of the movable member to a selected one of a plurality of maximum reciprocal movement amounts.
A power tool according to another aspect of the present invention includes a linear motor and a movable member region detector. The linear motor has a movable member driven to move reciprocally. The movable member has a tool connector and a position information region. The tool connector is for connecting work bits to the movable member. The movable member region detector detects the movable member position information region of the movable member.